In the field of biology or the like, conventionally, as described in the following patent literature 1, for example, there has been used a technique referred to as optical tweezers where a transparent micro bead is put into a liquid, the micro bead is captured at a focal point of a focused infrared laser beam, and DNA, a biological molecule, a cell or the like is manipulated in the liquid via the micro bead. Further, the following patent literature 2 discloses a technique where a resin-made micro structural body having a total length of 10 μm prepared by a two-photon absorption stereolithography is used as an object, and a cell is manipulated or a force is measured by driving the object using optical tweezers in a liquid.
In such a technique which uses optical tweezers, an object (specimen) is extremely minute and hence, it is necessary to manipulate the object in a liquid while observing the object using a microscope. In such a case, the object which is to be manipulated using the optical tweezers can be observed only 2-dimensionally using a usual microscope and hence, there arises a drawback that it is difficult to grasp the vertical relationship between the object and a focal point of an optical trap so that an accurate manipulation cannot be performed.
On the other hand, as a microscope which enables the 3-dimensional observation of an object to be observed, conventionally, a confocal microscope has been used. In the confocal microscope, an excitation laser beam is focused and irradiated to a specimen (an object to be observed to which fluorescent staining is applied) through an objective lens, and a fluorescent light emitted from the specimen is made to pass through a pin hole arranged at a conjugated position with the objective lens and is imaged on a detector. Light emitted from regions other than a focal point of the objective lens is eliminated by the pin hole and hence, only light in a focal region can be detected. Then, by 2-dimensionally scanning a focal point of the excitation laser beam on the specimen using a pair of galvano mirrors and an acousto-optic modulator and hence, a thin cross-sectional image of the specimen in the vicinity of an area at a specified depth can be obtained. Further, by scanning the objective lens or a specimen stage in the direction of an optical axis, cross-sectional images at different depths can be obtained. Accordingly, a 3-dimensional image of the specimen can be formed.
Further, with respect to the above-mentioned confocal microscope, as disclosed in the following patent literatures 3, 4, for example, there has been known a method where, to accelerate 2-dimensional scanning on a specimen, an excitation laser beam is split into a plurality of laser beams using a nipkow disc or a microlens array, and a plurality of regions on the specimen are simultaneously scanned. To achieve the substantially same purpose, as disclosed in the following patent literature 5, for example, there may be a case where aline-scanning-type scanning system where an excitation laser beam is scanned by focusing the laser beam in a line shape is used.
(PTL 1) JP-A-H8-234110
(PTL 2) JP-A-2009-294008
(PTL 3) JP-A-2009-210889
(PTL 4) JP-A-2010-160371
(PTL 5) JP-A-2010-164635